Within the following document, reference is made to numerous documents that provide further information related to subject matter being discussed. These references are listed at the end of the Detailed Description of the Preferred Embodiments and are identified by numbers in brackets [X], where X is the numerical identifier of a pertinent document. These documents are incorporated by reference in their entireties.
Self-assembled block copolymer thin films have attracted a great deal of attention recently as templates for nanolithography [1-9]. A diblock copolymer contains two immiscible polymer chains covalently bonded together and, on annealing, undergoes a microphase separation to form self-assembled periodic nanoscale domains. The domains can exist in various morphologies depending on the volume fractions of the two constituents of the polymer, including spheres, cylinders, and lamellae. The domain size and period scale with the molecular weight, making these materials useful masks for nanofabrication. Thin films of block copolymers have been used to pattern semiconductor dot and antidot arrays [1,2], metal dots and nanowires [3-6], magnetic storage media [7], and devices, such as capacitors, memory cells, and transistors have been fabricated using block copolymer lithography [8-9].
Successful implementation of block copolymer (BCP) patterning depends on the ability to control the morphology, orientation, and packing of the domains. Block copolymer domain patterns typically have good short-range order but lack long-range order. Long-range ordering has been accomplished by various approaches such as the application of external electrical fields [10,11], temperature gradients [12], shear fields [13], or by using chemically or topographically patterned substrates [14-21].
Most studies using patterned substrates have focused on the behavior of a monolayer of spherical or in-plane cylindrical block copolymer domains, or on short cylinders or lamellae oriented perpendicular to the surface. In addition, block copolymers have been confined within certain geometries such as pores or droplets [22-25], which introduce additional boundary conditions and can promote block copolymer morphologies not found in the bulk, such as the formation of concentric cylinders by lamellar block copolymers, or helical structures by cylindrical block copolymers.
As such, there has been difficulty obtaining block copolymer domain patterns that have good long-range ordering without requiring complex control or boundary conditions. There has been further difficulty obtaining additional geometries, such as square geometries, for block copolymer patterning. Accordingly, there is a need for a technique to obtain block copolymer domain patterns that have good long-range ordering and provide for enhanced geometries for such patterns.